Textile cord material and pneumatic tires manufactured therewith



United States Patent 3,419,060 TEXTILE CORD MATERIAL AND PNEUMATIC TIRES MANUFACTURED THEREWITH Ronald Stansfield Goy, Sutton Coldfield, England, assignor to Dunlop Rubber Company Limited, London, England, a British company No Drawing. Filed Nov. 6, 1964, Ser. No. 409,598 Claims priority, application Great Britain, Nov. 19, 1963, 45,538/63 4 Claims. (Cl. 152-359) ABSTRACT OF THE DISCLOSURE A synthetic hot stretched textile filamentary cord wherein each filament thereof in the finished form of the cord has a denier which is greater than thereby contributing superior resistance to buckling of the cord under axial compression loading.

My invention relates to textile cord material and to pneumatic tires manufactured therewith.

Steel cords made from a plurality of wires twisted together to form strands, the strands being twisted to form a cord, have been used in the manufacture of pneumatic tires for a considerable length of time and they are of advantage particularly in respect of their high tensile modulus (Youngs modulus) and their high resistance to buckling under axial load. Known textile cords are considered inferior to steel cords in these respects and it is an object of the invention to provide a synthetic textile filamentary cord which has an improved performance when compared with existing synthetic textile cords.

In the manufacture of synthetic textile filamentary cords, the filamentary size is usually kept to a minimum in view of the fact that spinning of the filaments is more convenient with a thin filament than with a thick one and, furthermore, the finished yarn is of ifiner texture which is more suitable for most purposes. In addition, while it is 'known to hot stretch nylon cords, to reduce subsequent tire growth, heat treatment is also carried out so as to prevent subsequent shrinkage of the material upon heating during vulcanisation and so as to set the material thus stabilizing its length.

According to my invention a synthetic textile filamentary cord comprises a plurality of filaments or monofilaments, having a denier greater than 10, twisted together, the cord having been heat-stretched to increase the tensile modulus of the cord and to increase the resistance of the cord to buckling under an axial compression load.

According to my invention also, a pneumatic tire comprises a tire building element, e.g. a rigid breaker, carcass, and a filler or chafer, incorporating synthetic textile filamentary cords as defined in the preceding paragraph.

Preferably a cord in accordance with the invention is formed from a polyester, and preferably the polyester is polyethylene terephthalate known as Terylene (registered Trademark). Alternatively the cord may be formed from polypropylene, rayon or nylon.

An embodiment of the invention will now be described by way of example.

A synthetic textile filamentary cord is made by spinning together 50 monofilaments of polyethylene terephthalate to form a yarn and twisting two of these yarns together to form the cord. The monofilaments are formed by a melt spinning process and a hot drawing process in known manner and have a denier of The cord is then subjected to a hot stretching process during which the cord is raised to a temperature near to the melting point of the constituent monofilaments and simultaneously stretched. This process may take place in a fluid bed such as is described in the specification of British Patent No. 885,513. Fluid beds are very effective in carryice ing out this process since high temperatures can be achieved without degradation of the material. As a result of this process the yarn denier is reduced but the filament denier remains substantially constant.

The cords are assembled in the form of a sheet, the cords being interconnected by a very weak weft material and, as is common in the tire-building art, the sheet of cords is treated with adhesive to increase the rubber-tocord bond strength and rubberised on both sides by means of a calender in known manner.

A pneumatic tire is constructed from a plurality of layers of these cords utilised in the breaker and/or carcass construction.

In one pneumatic tire construction, the cords in the carcass lie at to a circumferential line and the breaker comprises three layers of cords according to the invention, the cords in each of the layers being laid in a dilferent direction to the cords in any of the other layers and to the cords in the carcass.

In another pneumatic tire construction a 90 cord carcass is used and two, four or more, breaker layers are utilised, the cords in one layer crossing those in the next adjacent layer or layers and the cords being disposed at about 18 to the mid-circumferential plane of the tire.

It is an advantage to manufacture tires of the kind described above comprising cords according to the invention in view of the fact that the cords have, on the one hand, a high tensile modulus and, on the other hand, a high compressive modulus and increased resistance to buckling under axial compression loads compared with known textile cord material. The resulting tire has improved performance and wear characteristics compared with previously known textile tire constructions.

Having now described my invention, what I claim is:

1. A synthetic textile filamentary cord comprising two or more yarns twisted together, each 'of such yarns comprising a plurality of filaments each of which has a denier greater than 10, the cord having been heat-stretched to increase the tensile modulus of the cord and to increase the resistance of the cord to buckling under an axial compression load.

2. A pneumatic tire comprising a carcass of elastomeric material and a reinforcement in said carcass of a synthetic textile filamentary cord comprising two or more yarns twisted together, each of such yarns comprising a plurality of filaments each of which has a denier greater than 10, the cord having been heat-stretched to increase the tensile modulus of the cord and to increase the resistance of the cord to buckling under an axial compression load.

3. The pneumatic tire of claim 2 in which the cord is formed of a polyester.

4. The pneumatic tire of claim 3 in which the polyester is polyethylene terephthalate.

References Cited UNITED STATES PATENTS 2,273,200 2/1942 Hofi 57140 XR 2,324,583 7/1943 Jackson et al. 57-140 2,755,214 7/1956 Lyons et al. 152359 XR 2,991,817 7/1961 Gay et al l52359 XR 3,051,212 8/1962 Daniels 152330 3,195,603 7/1965 Ahles 152-359 2,235,867 3/1941 Castricum et al. 57140 XR 3,243,338 3/1966 Jackson 152-359 XR FOREIGN PATENTS 512,002 8/1929 Great Britain.

FRANK J. COHEN, Primary Examiner. D. E. WATKINS, Assistant Examiner.

US. Cl. X.R. 5714O 

